The Evolved Packet System (EPS) of the 3rd Generation Partnership Project (3GPP) consists of an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), a Mobility Management Entity (MME), a Serving Gateway (S-GW), and a Packet Data Network Gateway (P-GW) and a Home Subscriber Server (HSS).
The EPS supports interworking with a non-3GPP system (as shown in FIG. 1), wherein the interworking with the non-3GPP system is realized via an S2a/b/c interface, and the P-GW is taken as an anchor point between the 3GPP and the non-3GPP systems. In a system architecture diagram of the EPS, the non-3GPP system access is divided into untrusted non-3GPP access and trusted non-3GPP access; the untrusted non-3GPP access should be connected with the P-GW via an Evolved Packet Data Gateway (ePDG), and the interface between the ePDG and the P-GW is S2b; the trusted non-3GPP access can be connected with the P-GW directly via S2a interface, and the S2a interface uses Proxy Mobile IP version 6 (PMIPv6) to perform information exchange; in addition, the S2c interface has provided user-panel relevant control and mobility support between a user equipment (UE) and the P-GW, and the mobility management protocol supported thereby is Mobile IPv6 Support for Dual Stack Hosts and Routers (DSMIPv6), and it can be used for untrusted non-3GPP and trusted non-3GPP access.
The Wireless Local Area Network (WLAN) can access the EPS as a non-3GPP system, and this relates to the problem of an interconnection and interworking of the Fixed Mobile Convergence (FMC) concerned by many operators. The technique of interconnection and interworking and address allocation is as follows:
in the prior art, when the Residential Gateway (RG) is in a routing mode and supports that when Network Address (Port) Translation (NA(P)T) is N:1 (N is greater than or equal to 1), the RG can obtain the International Mobile Subscriber Identity (IMSI) or Network Access Identity (NAI) as the authentication party during performing an authentication based 3GPP Extensible Authentication Protocol (EAP). When establishing an NA(P)T entrance table, as shown in FIG. 2, the RG will establish an IMSI and a port number set (no port number will be allocated when N equals 1), and an association relationship of local IP addresses (abbreviated as: user identity association table), wherein the port number set (no port number is allocated when N equals 1) and the local IP addresses have been performed NA(P)T conversion by the RG Moreover, the RG also supports transferring the user identity association table to the Broadband Network Gateway/Broadband Remote Access Server (BNG/BRAS) via a Radius message. When the RG is in a bridge mode, the BNG/BRAS can obtain the IMSI/NAI during executing the authentication of EAP based 3GPP as an authenticator. In general, when the BNG/BRAS allocates a public network address to the mobile terminal as a local IP address, the BNG/BRAS establishes an association relationship between the IMSI/NAI and the local IP address, without containing the port number set; otherwise, the BNG/BRAS needs to support NA(P)T, and the association relationship should contain the port number set (as shown in FIG. 2).
In summary, in the scenario where the terminal access the EPC (Evolved Packet Core) via WLAN, if the RG is taken as a NA(P)T, especially in the scenario of N:1, the IP address acquired by the terminal is a private address allocated by the RG, and what is in communication with the exterior is the public address which has been converted by the RG, in addition to the port number. Since the terminal may have different services, and different services occupy different port numbers, that is, when a terminal has a plurality of services at the same time, what identifies the terminal is a public IP address in addition to a port number set. When another terminal accesses the RG, the address converted by the RG is also the IP public address, but the sets of the port numbers thereof are different. The public address and port number set will be reported to the BNG/BRAS/AAA.
The service offload technique is as follows: the terminal introduced in above-mentioned interconnection and interworking part has a plurality of services at the same time which comprise the service being offloaded from the WLAN and the service being routed via the EPC. The case of the service being offloaded by the WLAN and the service being routed via the EPC are as follows: because of the diversity service requirements of user, the user accesses a plurality of services at the same time; if all the services pass through the core network of 3GPP, which not only increases the data traffic load of the core network but also results in that the plurality of services preempt limited network resources, the quality of the service which has high requirement for the QoS cannot be guaranteed. Therefore, it is necessary to effectively implement the service offload. Taking S2b as an example, as shown in FIG. 3, for the operators, a portion of services can be transmitted via the EPS, and the other portion of services (for example: Internet service, the service on the stream media service platform of the mobile network is also included) can be offloaded by the WLAN, according to the features of the services, so that the traffic load of the 3GPP core network is reduced.
Different services be offloaded by the WLAN occupy a plurality of different port numbers in the above-mentioned port number set, as all being in an IPsec tunnel package, data packets routed by the EPC will occupy one port number in the port number set.
The policy control technique is as follows: with the trend of the FMC architecture being deeply converged, when the mobile terminal directly implements service offload via a WLAN, the PCRF server of the 3GPP network will still issue a particular policy control or charging rules related with the mobile terminal to a fixed network. For example, a policy control or charging and so on is performed according to a particular service type of a certain mobile terminal; after receiving the policy rules of the policy control server or the charging rules of the charging server, the network element of the fixed network will carry out collection of policy control or charging information related with the particular mobile terminal.
In order to support issuing the policy related with the particular mobile terminal to the BNG/BRAS, a policy session is established by the Broadband Policy Control Function (BPCF), the BPCF establishes a session with the PCRF of 3GPP, acquires the policy from the PCRF, and issues the policy to the BNG/BRAS.
In the case where the service offloaded by WLAN is from a stream media service platform of a mobile network, in the relevant art, when the Application Function (AF) receives a service establishment request from a mobile terminal, or when a Traffic Detection Function (TDF) detects service information, interaction with the PCRF will be performed to request the PCRF for a policy whether the service is accepted.
However, if it is desirable to perform user-level management and control on data directly routing from the BNG/BRAS to the Internet/PDN, the BPCF needs to be able to download a user-based policy from the PCRF and to be able to report user-based information to the PCRF; moreover, the PCRF establishes an Rx session/AF session with the AF (or the PCRF establishes an Sd session/TDF session with the TDF), and the PCRF establishes an S9* session with the fixed network; and the PCRF needs to be able to perform an user-level session binding before transmitting the policy (same demand exists for the scenarios of a BPCF binding AF session/Rx session (or Sd session/TDF session) to a fixed network policy session). The above-mentioned S9* session can also be called S9a session, and an S9* interface is also called S9a interface; and the S9a session refers to a gateway control session or an IP-CAN session, or refers to both at the same time, on the S9a interface.
Referring to the association mechanism, shown in FIG. 4, between the AF session/Rx session (or Sd session/TDF session) and an S9* session, traditional methods for session binding by the policy control and charging technique are: session binding according to IP address management, or session binding according to an user identity (for example, IMSI or NAI), or session binding according to a PDN identification (for example, APN). But herein, the information mentioned above is not enough, because there is neither user identity nor APN information on the Rx/Sd. Although there is IP address information, the IP address of the terminal is public, and is a public address using by a plurality of UEs accessed to the same RG (see the above-mentioned analysis). Therefore, session binding purely according to the addresses will lead to mistakes.
It can be seen from the above-mentioned analysis that, for the scenario where the mobile terminal accesses a mobile network service directly via a fixed network, a problem of inaccurate session binding exists in the above-mentioned method for session binding; and aiming at the problem of inaccurate session binding exists in the scenario where a mobile terminal accesses a mobile network service directly via a fixed network in the relevant art, no effective solution is proposed yet at present.